41. Are there limits on the amount a candidate can spend?

Source: 

Regulation of Election Expenditure Act No. 3 of 2023, Section 3 (1) and 4 (1)

3. (1) Within a period of five days after the conclusion of the period of nomination specified in the Proclamation or Order requiring the conduct of an election under any law specified in section 2, the Election Commission shall, in consultation with the recognized political parties, and the independent groups contesting such election, fix by Order published in the Gazette, a sum of money in Sri Lankan rupees to be used for the purpose of calculating an authorized amount, in accordance with the provisions of this section, for such election:
Provided however, in the case of a presidential election, every candidate who has not been nominated by a political party shall be consulted.

4. (1) A recognized political party, an independent group and a candidate at an election conducted under any law specified in section 2, shall not incur expenditure in excess of the authorized amounts referred to in subsections (3) and (4) of section 3 as the case may be, in respect of such election.

https://www.parliament.lk/uploads/acts/gbills/english/6287.pdf 

There is a limit on the amount a candicate can spend. However, it is not a fixed amount. The Election Commission of Sri Lanka collaborates with political parties and (during a presidential election), candidates who are not nominated by a political party to decide a per-voter rate, which needs to be done within  five days after the conclusion of the period of nomination