Within three months after the expiration of the time allowed for the filing of objections to claims, the trustee must render, under oath, to the register or clerk an account charging himself with all the moneys of the trust estate which have come into his possession, or with which he is chargeable, and crediting himself with all sums to which he is entitled as credits, and must file therewith the vouchers on which he relies to sustain such credits. A similar account must be filed every six months thereafter.