What do you do when you find a major error in the expenses or any report?

After greeting ,,,

You must first ensure the existence of errors and re-audited more than once. In case you need to make sure to recognize the mistake if you or someone else is not the cause of the emitter is in the wrong

Then re-correct the error in the report, and if the work was under constraint can correct the error that is reversed limitation.

In case if the error is related to the interests of the government as taxes must tell them so error correction together.

First of all, evaluate the relevance of the error whether it makes a material impact in the financials or not. Assuming a material impact, passed the reversal effect of the same considering the suitable IFRS applicability to maintain the financials in true and fair view.

After rectifying the error, test the control procedures to avoid such mistakes or errors in the future.

Yes, mistakes should be corrected but many depends on the level of significance (just like in audit case).

Thanks for the invitation. 

In general errors could be corrected , however, the role depends on someone position in the organization. 

Control check should be applied (Check & Maker).

view the report again then check once again to find the mistake.