[17] In 1911 Ion Lapedatu became director of the newly established "General Assurance Bank" (Banca Generală de Asigurare) in Sibiu.

[18] On 1 January 1922 he was appointed Professor at the Chair for Public and Private Finances of the Academy for High Commercial Studies and Industry in Cluj, a position he held until 1938.

[19][20] He had numerous appointments to various administrative councils, among which at the Albina Bank in Sibiu, at the Gojdu Foundation, and since 1925 at SONAMETAN, the national corporation established to exploit the methane gas deposits discovered in Transylvania, where he became Chairman.

[26] He received his first political appointment as general secretary of the finance department in the "Directory Council of Transylvania, Banat and the Romanian Counties in Hungary" (Consiliul Dirigent al Transilvaniei, Banatului și ţinuturilor românești din Ungaria).

[19] Lapedatu joined early the Romanian National Party in Transilvania and Banat (Partidul Național Român din Ardeal).

He left it in 1926 together with Vasile Goldiș and Ioan Lupaș before its merger with the Peasants' Party (Partidul Țărănesc) when he became Finance Minister in the Government of Alexandru Averescu (1926-1927).

[32][33][34] He was elected in 1906 secretary of the "Romanian Banks Delegation" (Delegațiunea băncilor române) acting in between conferences; in this position he drove the development of the initiative from a consultative to an executive role.

He elaborated the statutes of the future "Solidaritatea" Association in compliance with the Hungarian financial law in effect at that time, enrolled the support required for having it registered and approved in 1907; he became its secretary.

He embraced the idea of a Romanian insurance bank launched at the Conference of the Directors and, in his quality as secretary of "Solidaritatea", launched an appeal in the conference of 27 September 1909, elaborated the feasibility study, advocated the initiative both with potential participants and with the authorities, and published "clarifications" in the "Economic Review", explaining that the Romanian population was not able to meet the conditions imposed by the institutions already existent in Transylvania, and in particular in Sibiu, either founded locally by Saxons or Hungarians, or established as branches of insurance companies from Austria, Germany, Italy or France.

[47][19][48] Upon a request from the Ministry of External Affairs, he interrupted in November 1921 his mission to Budapest for a few weeks in order to join the Romanian delegation at the "Paris Reparations Commission" addressing the partition of the Austrian-Hungarian public debt.

[19] In 1922 he was a member of the Romanian delegation in the Conference of the Successor States of the Former Habsburg monarchy in Rome, mandated to solve together with the Austrian and Hungarian representatives the issues arising from the peace treaties.

[49][50][51][52][53] In 1930, Lapedatu was elected as President of the Romanian delegation to address the question of the Gojdu Foundation, following the agreement between the Ministries of External Affairs of Romania and Hungary; he reached an amiable solution in 1936, ratified on 5 May 1938 by King Carol II of Romania and on 20 June 1940 by Regent Miklós Horthy of Hungary; it could not be enforced in the aftermath of the Second Vienna Award, and as of 2025 the issue is still open.

He was also a member in the "Turing Club of Romania", in "Admir", in the Hungarian "Brașov Touring Association", and in the "Enczian" society of the young Hungarian hand workers in Brașov; in addition, he was long time President of the Cultural and Sportive Association of BNR Employees, he described his ideas and his experience in the inaugural speech delivered at the opening of the BNR Chalet at Diham in 1945.

Ion Lapedatu provided significant financial means to support artists, national schools and churches, among which the Administration of the Central Romanian Orthodox Schools (Romanian: Eforia Școalelor Centrale Ortodoxe Române) in Brașov, the Central High Commercial School in Brașov,[67] the orthodox cathedral in Orăștie, the monument of WWI heroes in Săcele, the restoration of patrimony monuments including the monasteries Curtea de Argeș and Aninoasa, and the Golești architectural complex.

In 1918, as Ion Lapedatu stopped his activity to dedicate his time and energy to the integration of Transylvania in the united Romania, the Foundation and its patrimony were transferred to the "Trade Union of Transylvanian Journalists".

[79][80] After a bus accident from 1947, he was immobilized in bed; for this reason he was not arrested in the night of 5/6 May 1950 in the so-called "group of dignitaries", like his brother Alexandru, although he was under investigation by the Securitate.