The National Children's Bureau is selling its north London offices as part of a £1m restructure.
The charity says its current premises are "not fit for purpose" and it will complete a move within the capital early next year.
Figures published this week in the charity’s latest annual report, for the year to the end of March 2017, show the largest proportion of the £1m spent on restructuring during the year related to the sale of the freehold on its headquarters.
Other restructuring costs included £334,000 on making 16 staff redundant, made up of £133,000 on termination costs plus a further £201,000 on salary costs relating to their notice periods.
The total number of staff employed by the charity fell from 106 to 98, the accounts show, while spending on staff salaries rose from £4.4m to £4.6m.
The NCB, which carries out research and campaigns on aspects of child policy, has exchanged contracts with the developer, with completion expected in early 2018.
The freehold land and buildings are valued at £7.5m, according to the documents.
Anna Feuchtwang, chief executive of the NCB, told Third Sector: "In 2016/17, the National Children’s Bureau conducted a restructure of the organisation to give us an efficient and sustainable shape to deliver our charitable aims. The key objective was to ensure the long-term sustainability of the organisation, and we put in place measures to keep our core costs to a minimum and bring them in line with available funding".
"As part of this work we took forward plans to sell our existing offices in London, which are not fit for purpose and incur high costs for maintenance and upkeep," she said. "We will be investing and moving into new premises in London in 2018, and we are considering a number of options."
The accounts also show a small drop in the charity's total income compared with last year, from £20.7m to £19.4m.
Feuchtwang is paid £99,470, the accounts show.
The NCB was established in 1963 to address the plight of neglected children. Its current campaigning and advocacy focuses on early years opportunities, children's health and wellbeing, and the rights of disabled and vulnerable children.
It provides the secretariat to the All-party Parliamentary Group for Children, which is chaired by the former children's minister Tim Loughton.